The invention relates to a device for adjusting camber and/or toe of a vehicle wheel of a motor vehicle.
In a generic motor vehicle with a wheel suspension, the rotary parts of an actuating member are determinative for the camber and/or toe of the vehicle wheel and adjusted via actuators (for example a spur gear mechanism) and electric motors in both rotation directions in opposite directions or in same direction. However, it must be ensured that reaction torques from the dynamic or static wheel loads do not cause unwanted adjustment. Such reaction torques are transmitted by the rotary parts of the actuating element via a gear stage to a drive motor. This means that the drive motor is required to continuously provide a counter torque (during operation partly with changing directions) in order to maintain the set target position of the two rotary parts. If the set target position of the rotary parts should be maintained also when the vehicle is parked, even in this case there would be a need to apply the counter torque, i.e. the drive motor has to be acted upon by a holding energy.
DE 10 2009 031 344 A1 discloses a generic device having a wrap spring brake interposed in driving relationship between the drive motor and the actuating element for camber and/or toe adjustment. Using the wrap spring brake, a torque transmission can be enabled from the drive motor to the actuating element. Conversely, the wrap spring brake blocks a transmission of reaction torques in the opposite direction without external energy.
The structure of the wrap spring brake and the resultant problem will now be described: The wrap spring brake includes on the input side and output side an opening part and a closing part, respectively, which formfittingly engage in both rotation directions with one another in the presence of a circumferential clearance. Moreover, a wrap spring is provided having spring legs, respectively projecting between the opening part and the closing part. The wrap spring brake is configured so as to assume its locking position only after building up a reaction torque that acts from the actuating element in direction of the drive motor, in which locking position a further transfer of the reaction torque is blocked. Such a transition to the locking position is implemented as a result of an expansion of the wrap spring when acted upon by the reaction torque. This generates a friction fit with an outer sleeve, sufficient to prevent a torque transmission to the electric motor. In the DE 10 2009 031 344 A1, the transition of the wrap spring to its locking position is realized only after buildup of the reaction torque so that there is a risk that the reaction torque acts upon the drive motor before reaching the locking position, possibly causing the actuating element to move from its target position.